Light emitting diodes (“LEDs”) emit light when forward biased. LEDs employ field effects as a light emitting principle. LEDs have an even longer life span than that of incandescent lamps. LEDs may emit various colors of light from ultraviolet rays through visible light up to infrared rays. The first visible LEDs were developed in 1962 by Nick Holonyak who was a professor at the University of Illinois. LEDs are currently used for various purposes and expected to replace fluorescent lamps or incandescent lamps in near future.
Like general semiconductor chips, an LED chip needs to be packaged to be mounted on a PCB (“Printed Circuit Board”). As LED packages are made smaller and thinner, there is an effort to save costs of process and investment by changing existing WL (“Wafer Level”) to CS (“Chip Scale”). Accordingly, packaging is performed in a wafer-to-wafer bonding process differently from the existing packaging process that is performed by connecting lead frames with the chip through wire bonding or die bonding. By doing so, the number of steps required in a manufacturing process may be decreased and the number of packages per wafer may be increased.
FIG. 1 is a cross sectional view illustrating a package manufactured in a conventional wafer-to-wafer bonding method. Referring to FIG. 1, the package includes a sapphire substrate 100, a patterned layer 110 grown on the sapphire substrate 100, a conductive layer 120 (hereinafter, referred to as “first conductive layer”) formed on the patterned layer 110, an insulating layer 130, a conductive layer 140 (hereinafter, referred to as “second conductive layer”) formed on the insulating layer 130 and brought in contact with the first conductive layer 120, a conductive layer 150 (hereinafter, referred to as “third conductive layer”) passing through the insulating layer 130 and electrically connecting the first conductive layer 120 with the second conductive layer 140. In the conventional package, since the first conductive layer 120 is brought in contact with the second conductive layer 140 upon the wafer-to-wafer bonding, a void is created between a chip and the insulating layer. Such a void may weaken attachment strength.
FIG. 2 is a view illustrating a process of manufacturing a package in a conventional wafer-to-wafer bonding method. Referring to FIG. 2, the insulating layer 130 is first prepared. The insulating layer 130 may be an Si layer, an AlN layer, or an Al2O3 layer. Thereafter, a via hole 160 is formed through the insulating layer and plated to form the third conductive layer 150. Then, the second conductive layer 140 is formed on the insulating layer 130 and the third conductive layer 150, and wafer-to-wafer bonded with a chip including the patterned layer 110 and the first conductive layer 120 sequentially formed on the sapphire substrate 100. In the conventional LED package and the method of manufacturing the LED package, the Si substrate has excellent flatness compared to other substrates, but has disadvantages of a long process time and a high material cost for substrate production. The ceramic substrate, such as AlN or LTCC substrate, has a lower material cost than that of other substrates, but has a relatively long process time and poor flatness. Further, as described above, there is a problem that a void occurs between the chip and the insulating layer. Accordingly, there is a need for a package that has a reduced process time and a high flatness while enhancing attachment strength and a method of manufacturing the package.